To resolve this problem, various methods have been proposed by the prior art.
Japanese Patent Laid-Open Publication 52/80099, suggests staggering the times that power is supplied to the loads.
Japanese Utility Model Publication 55/8056 suggests providing the heater for boiling water with a phase control circuit, and regulating the heater current by the phase control circuit.
Japanese Patent Laid-Open Publication 59/231694 suggests detecting the input current of the vending machine, and controlling the heater current in relation to a change of the input current.
However, with the prior art methods of staggering the load and providing a phase control circuit, effective use of the heater cannot be achieved because of the length of time required to heat the water to a predetermined temperature in order to obtain adequately hot water.
With the prior art method of detecting the input current, since power is supplied to the heater even when the compressor is started, the power is reduced due to the line drop so that it takes a long time to start the compressor. Further, since all of the input current, having been phase controlled, is necessarily detected, the amount of the detected current would be unstable.